1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License, Version 1.0 only 6 * (the "License"). You may not use this file except in compliance 7 * with the License. 8 * 9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 10 * or http://www.opensolaris.org/os/licensing. 11 * See the License for the specific language governing permissions 12 * and limitations under the License. 13 * 14 * When distributing Covered Code, include this CDDL HEADER in each 15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 16 * If applicable, add the following below this CDDL HEADER, with the 17 * fields enclosed by brackets "[]" replaced with your own identifying 18 * information: Portions Copyright [yyyy] [name of copyright owner] 19 * 20 * CDDL HEADER END 21 */ 22 /* 23 * Copyright 2004 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 /* 28 * Debugger co-routine context support: In order to implement the context- 29 * switching necessary for MDB pipes, we need the ability to establish a 30 * co-routine context that has a separate stack. We use this stack to execute 31 * the MDB parser, and then switch back and forth between this code and the 32 * dcmd which is producing output to be consumed. We implement a context by 33 * mapping a few pages of anonymous memory, and then using setcontext(2) to 34 * switch to this stack and begin execution of a new function. 35 */ 36 37 #include <mdb/mdb_context_impl.h> 38 #include <mdb/mdb_modapi.h> 39 #include <mdb/mdb_debug.h> 40 #include <mdb/mdb_err.h> 41 42 #include <sys/types.h> 43 #include <sys/mman.h> 44 45 #include <ucontext.h> 46 #include <unistd.h> 47 #include <setjmp.h> 48 #include <fcntl.h> 49 #include <errno.h> 50 51 static void 52 context_init(mdb_context_t *volatile c) 53 { 54 c->ctx_status = c->ctx_func(); 55 ASSERT(c->ctx_resumes > 0); 56 longjmp(c->ctx_pcb, 1); 57 } 58 59 mdb_context_t * 60 mdb_context_create(int (*func)(void)) 61 { 62 mdb_context_t *c = mdb_zalloc(sizeof (mdb_context_t), UM_NOSLEEP); 63 size_t pagesize = sysconf(_SC_PAGESIZE); 64 int prot = sysconf(_SC_STACK_PROT); 65 static int zfd = -1; 66 67 if (c == NULL) 68 return (NULL); 69 70 if (prot == -1) 71 prot = PROT_READ | PROT_WRITE | PROT_EXEC; 72 73 c->ctx_func = func; 74 c->ctx_stacksize = pagesize * 4; 75 c->ctx_stack = mmap(NULL, c->ctx_stacksize, prot, 76 MAP_PRIVATE | MAP_ANON, -1, 0); 77 78 /* 79 * If the mmap failed with EBADFD, this kernel doesn't have MAP_ANON 80 * support; fall back to opening /dev/zero, caching the fd, and using 81 * that to mmap chunks of anonymous memory. 82 */ 83 if (c->ctx_stack == MAP_FAILED && errno == EBADF) { 84 if (zfd == -1 && (zfd = open("/dev/zero", O_RDWR)) >= 0) 85 (void) fcntl(zfd, F_SETFD, FD_CLOEXEC); 86 87 if (zfd >= 0) { 88 c->ctx_stack = mmap(NULL, c->ctx_stacksize, prot, 89 MAP_PRIVATE, zfd, 0); 90 } 91 } 92 93 c->ctx_uc.uc_flags = UC_ALL; 94 if (c->ctx_stack == MAP_FAILED || getcontext(&c->ctx_uc) != 0) { 95 mdb_free(c, sizeof (mdb_context_t)); 96 return (NULL); 97 } 98 99 c->ctx_uc.uc_stack.ss_sp = c->ctx_stack; 100 c->ctx_uc.uc_stack.ss_size = c->ctx_stacksize; 101 c->ctx_uc.uc_stack.ss_flags = 0; 102 c->ctx_uc.uc_link = NULL; 103 makecontext(&c->ctx_uc, context_init, 1, c); 104 105 return (c); 106 } 107 108 void 109 mdb_context_destroy(mdb_context_t *c) 110 { 111 if (munmap(c->ctx_stack, c->ctx_stacksize) == -1) 112 fail("failed to unmap stack %p", c->ctx_stack); 113 114 mdb_free(c, sizeof (mdb_context_t)); 115 } 116 117 void 118 mdb_context_switch(mdb_context_t *c) 119 { 120 if (setjmp(c->ctx_pcb) == 0 && setcontext(&c->ctx_uc) == -1) 121 fail("failed to change context to %p", (void *)c); 122 else 123 fail("unexpectedly returned from context %p", (void *)c); 124 } 125 126 jmp_buf * 127 mdb_context_getpcb(mdb_context_t *c) 128 { 129 c->ctx_resumes++; 130 return (&c->ctx_pcb); 131 } 132